1. Field of the Invention
The present invention generally relates to a system to control a chassis vibration damping device in a vehicle.
2. Background Information
To make it possible to more effectively adjust the vibration damping characteristics of a motor vehicle chassis to the conditions under which the vehicle is being driven or to the condition of the road, known devices modify the damping force characteristic of individual vibration dampers, or of all the vibration dampers, of the chassis. German Patent Number DE-A-41 36 224 (which is equivalent to British published application number GB-OS 2 253 460 A), for example, uses a number of sensors to measure or to calculate operating parameters of the motor vehicle which are representative of the instantaneous damping force demand. The damping force demand variables determined in real time are converted on the basis of vehicle-specific evaluation functions into a number of control variables, the sum of which is representative of the damping force characteristic to be set in the vibration dampers.
Specifically, in the known damping force control system, the damping force characteristic is selected as a function of the instantaneous values of the transverse acceleration, the transverse jerk, the thrust (longitudinal force), the change in thrust, the frequency-weighted superstructure acceleration and the frequency-weighted wheel acceleration.
The damping force characteristic refers to a relationship between the damping force produced by the damper as a function of the velocity of the damper compression and/or extension. The damping force characteristic can be shifted in several stages or can be adjusted continuously, for example between a "hard" damping force characteristic with a high damping force which changes comparatively sharply as a function of the damper velocity, through a "medium" damping force characteristic into a "soft" damping force characteristic, in which the damping force is on a lower level and changes less sharply as a function of the damper velocity. To prevent an excessively frequent shifting between the different damping force characteristics, there is a hysteresis device which delays the shifting of the characteristic from "hard" to "soft", but not from "soft" to "hard".
In the known damper control system, a plurality of sensors are necessary to measure the information which relates to the vehicle movement in the three spatial axes or the three axes of movement of the vehicle--the longitudinal axis, the transverse axis and the vertical axis--by means of corresponding acceleration sensors, and/or from measurement signals provided by substitute or auxiliary sensors which measure the steering angle, the vehicle speed, the angle of the throttle plate, the engine speed, the brake pressure etc.
German Patent No. 41 30 090 discloses a method for the automatic determination of the correspondence between directionally-related sensors and the directions of movement of a vehicle, whereby the output signals are transmitted to an evaluation unit. The two sensors are orthogonal to one another and, if possible, are parallel to one direction of vehicle movement.